1. Strabismus, Amblyopia & Leukocoria
Dr. Hessah Alodan,
Pediatric Opthalmology Dept, KAUH

2. Why Two Eyes ?
You can demonstrate to a patient the difference in their field or their child's field with one eye compared to two. With two eyes you can also demonstrate the peripheral field and the central fusion.

3. Why Two Eyes ? Left Eye Monocular Right Eye Monocular Binocular
Total binocular field is nearly 170 degrees (varies according to configuration of orbits)

4. Why Two Eyes ? Two Pencils Test
The same person with one eye closed or with manifest strabismus or no stereopsis will miss the examiner's pencil initially and place it correctly only after the second or third try.
With both eyes open the patient who uses both eyes producing stereopsis can put his pencil accurately on the examiner's pencil if stereopsis is present

5. Visual Axis Binocular Vision
Imaginary line between fovea and the object
Binocular Vision
If the visual axises from both eyes intersect at the object, binocular vision occurs

6. Sensory Fusion Motor Fusion
Supper imposed images from each corresponding retinal area in binocular cells at the level of the occipital cortex
Same images
Similar in size
Similar in clarity
Motor Fusion
Ability to physically move the eyes so that they are pointing in the same direction allowing the corresponding areas of the retina in each eye to be pointing at the object of regard

7. Visual Axes Misalignment lead to:
Confusion
Superimposition of the two different images stimulating corresponding retinal points
Diplopia
One object stimulating two none corresponding retinal points

8. Compensatory mechanism to misalignment of VA :
Suppression
Subconscious active neglect of one eye input that occurs only when both eyes are open
Amblyopia

9. Action of extraocular muscles
All obliques
Abduct
Horizontal Recti
Adduct 
All superior muscles 
Intort
 All inferior muscles 
Extort
Action
Muscles
    Dextroelevation 
OD: Superior Rectus OS: Inferior Oblique
  Dextrodepression
OD: Inferior Rectus    OS: Superior Oblique
    Levoelevation
OD: Inferior Oblique  OS: Superior Rectus
    Levodepression
OD: Superior Oblique  OS: Inferior Rectus
       Right gaze
OD: Lateral Rectus  OS: Medial Rectus
        Left gaze
OD: Medial Rectus  OS: Lateral Rectus

10. What is Strabismus ?
Ocular misalignment due to abnormality in binocular vision or anomalies in neuromuscular control of ocular motility

11. Classification of Strabismus:
According to fusion status
Phoria
Latent tendency of the eye to deviate and controlled by fusional mechanism
Intermittent Phoria
Fusion control is present part of the time
Tropia
Manifest misalignment of the eye all the time

12. Classification of Strabismus:
According to fixation
Alternating
Spontaneous alternation of fixation from one eye to the other
Monocular
Preference of fixation with one eye

13. Classification of Strabismus:
According to type of deviation
Horizontal
Esodeviation
Exodeviation
Vertical
Hyperdeviation
Hypodeviation
Torsional
Incyclodeviation
Excyclodeviation
Combined

14. Classification of Strabismus:
According to age of onset
Congenital
Acquired

15. Classification of Strabismus:
According to variation of the deviation with gaze position or fixing eye
Comitant
Same deviation in different direction of gaze
Incomitant
Variable deviation in different direction of gaze usually in paralytic or restrictive type of strabismus

16. Examination History Inspection Assessment of monocular eye function
Visual acuity
Preverbal children
CSM
OKN
Preferential looking
Visual evoked potential

17. Examination Assessment of monocular eye function Visual acuity
Verbal children
Symbol tests
Single illiterate E
Allen pictures
H O T V letters

18. Examination Assessment of binocular eye function Hirschberg test
Krimski’s test
Cover test
Alternate cover test
Prism cover test

19. Examination Fundoscopy Cycloplegic refraction Tropicamide
Cyclopentolate
Atropin

20. Type of Strabismus Esotropia Pseudoesotopia Infantile esotropia
Accommodative esotropia
Partially accommodative esotropia

21. Pseudoesotropia
Occur in patients with flat broad nasal bridge and prominent epicanthal fold
Gradually disappear with age
Hirschberg test differentiate it from true esotropia

22. Infantile Esotropia
Common comitant esotropia occur before six month of age
Deviation is often large more than 40 prism diopter
Frequently associated with nystagmus and inferior oblique over action
Treatment
Correction of refractive error
Treat amblyopia
Surgical correction of strabismus

23. Accommodative Esotropia
Occur around 2 ½ years of age
Start as intermittent then become constant
High hypermetropia
Treatment
Full cycloplegic correction
Treat amblyopia

24. Partially Accommodative Esotropia
Improve partially with glasses
Treatment
Full cycloplegic correction
Treat amblyopia
Surgical correction of strabismus

25. Type of Strabismus Exotropia Intermittent exotropia Constant exotropia
Sensory exotropia

26. Intermittent exotropia
Onset of deviation within the first year of age
Closing one eye in bright light
Usually not associated with any refractive error
Usually not associated with amblyopia
Treatment
Correction of any refractive error
Surgical correction of strabismus

27. Constant exotropia
Maybe present at birth or maybe progress from intermittent exotropia
Treatment
Correction of any refractive error
Correction of amblyopia
Surgical correction of strabismus

28. Sensory exotropia
Constant exotropia that occur following loss of vision in one eye e.g trauma
Treatment
Correction of any organic lesion of the eye
Correction of amblyopia
Surgical correction of strabismus

29. Types of Strabismus Paralytic strabismus 6th nerve palsy
3rd nerve palsy

30. 6th Nerve Palsy Incomitant esotropia Limitation of abduction
Abnormal head position

31. 4th Nerve Palsy Congenital or acquired
Hypertropia of the affected eye with excyclotropia
Abnormal head position

32. 3rd Nerve Palsy Congenital or acquired
Exotropia with Hypotropia of the affected eye
In children caused by: trauma, inflammation, post viral and tumor
In adult caused by: aneurysm, diabetes, neuritis, trauma, infection and tumor

33. Special Types of Strabismus
Duane strabismus
Brown syndrome
Thyroid opthalmopathy

34. Duane Syndrome Limitation of abduction Mild limitation of adduction
Retraction of the globe and narrowing of the palpebral fissure on adduction
Upshoot or downshoot on adduction
Pathology faulty innervation of the lateral rectus muscle by fibers from medial rectus leading to co-contraction of the medial rectus and lateral rectus muscles

35. Duane Syndrome Limitation of abduction Mild limitation of adduction
Retraction of the globe and narrowing of the palpebral fissure on adduction
Upshoot or downshoot on adduction
Pathology faulty innervation of the lateral rectus muscle by fibers from medial rectus leading to co-contraction of the medial rectus and lateral rectus muscles

36. Brown Syndrome Limitation of elevation on adduction
Restriction of the sheath of the superior oblique tendon
Treatment needed in abnormal head position or vertical deviation in primary position

37. Thyroid Ophthalmopathy
Restrictive myopathy commonly involving inferior rectus, medial rectus and superior rectus
Patients presents with hypotropia, esotropia or both

38. Surgery of Extraocular Muscle
Recession : weakening procedure where the muscle disinserted and sutured posterior to its normal insertion

39. Surgery of Extraocular Muscle
Resection : strengthening procedure where part of themuscle resected and sutured to its normal insertion

40. Complication of Extraocular Muscle Surgery
Perforation of sclera
Lost or slipped muscle
Infection
Anterior segment anesthesia
Post operative diplopia
Congectival granuloma and cyst

41. Amblyopia

42. What is Amblyopia ?
Amblyopia refers to a decrease of vision, either unilaterally or bilaterally, for which no cause can be found by physical examination of the eye

43. Pathophysiology of Amblyopia
amblyopia is believed to result from disuse from inadequate foveal or peripheral retinal stimulation and/or abnormal binocular interaction that causes different visual input from the foveae
Cortical ocular dominance columns representing amblyopic eye less responsive to stimulus and show changes microscopically
Lateral geniculate layers subserving amblyopic eyes atrophic
Afferent pupil response has been reported but not common
No retinal changes - ERG OK

44. Amblyopia
Three critical periods of human visual acuity development have been determined. During these time periods, vision can be affected by the various mechanisms to cause or reverse amblyopia. These periods are as follows:
The development of visual acuity from the 20/200 range to 20/20, which occurs from birth to age 3-5 years.
The period of the highest risk of deprivation amblyopia, from a few months to 7 or 8 years.
The period during which recovery from amblyopia can be obtained, from the time of deprivation up to the teenage years or even sometimes the adult years

45. Amblyopia
Diagnosis of amblyopia usually requires a 2-line difference of visual acuity between the eyes
Crowding phenomenon: A common characteristic of amblyopic eyes is difficulty in distinguishing optotypes that are close together. Visual acuity often is better when the patient is presented with single letters rather than a line of letters
An amblyopic eye with 20/70 full line vision
may be able to see as well
20/30 viewing a single optotype
to 20/70

46. Causes of Amblyopia Anisometropia
Many causes of amblyopia exist; the most important causes are as follows:
Anisometropia
Inhibition of the fovea occurs to eliminate the abnormal binocular interaction caused by one defocused image and one focused image.
This type of amblyopia is more common in patients with anisohypermetropia than anisomyopia. Small amounts of hyperopic anisometropia, such as 1-2 diopters, can induce amblyopia. In myopia, mild myopic anisometropia up to -3.00 diopters usually does not cause amblyopia.

47. Causes of Amblyopia Strabismus
The patient favors fixation strongly with one eye and does not alternate fixation. This leads to inhibition of visual input to the retinocortical pathways.
Incidence of amblyopia is greater in esotropic patients than in exotropic patients
Alternation with alternate suppression avoids amblyopia

48. Causes of Amblyopia Visual deprivation
Amblyopia results from disuse or understimulation of the retina. This condition may be unilateral or bilateral. Examples include cataract, corneal opacities, ptosis, and surgical lid closure
Deprivation Amblyopia
Bilateral Deprivation Amblyopia

49. Causes of Amblyopia Organic
Structural abnormalities of the retina or the optic nerve may be present. Functional amblyopia may be superimposed on the organic visual loss

50. Causes of Amblyopia Ametropic Amblyopia
Uncorrected high hyperopia is an example of this bilateral amblyopia.

51. Treatment
The clinician must first rule out an organic cause and treat any obstacle to vision (eg, cataract, occlusion of the eye from other etiologies).
Remove cataracts in the first 2 months of life, and aphakic correction must occur quickly
Treatment of anisometropia and refractive errors must occur next
The next step is forcing the use of the amblyopic eye by occlusion therapy